1. Field of the Invention
The present invention relates to an endoscope system used by being inserted into a suspected substance, and more particularly to an endoscope system that transmits video signals via an optical fiber. Priority is claimed on Japanese Patent Application No. 2010-220157, filed on Sep. 30, 2010, the content of which is incorporated herein by reference.
2. Description of Related Art
Conventionally, typical endoscope systems utilizes a method in which video signals output from the image pickup device provided on a distal end portion of the endoscope to be inserted into a suspected substance are transmitted as analog signals to a video processor. Because typical endoscopes have a total length of several meters, the analog video signals are influenced by external noise during their transmission. As a result, the S/N ratio tends to be decreased, resulting in deteriorated image quality. In particular, in the medical front and the like that uses an endoscope system, a unit such as an electrosurgical knife is in operation. Therefore, noises at levels that are not present in a normal environment fly around, and their influences are extremely enormous.
To resolve this problem, Japanese Unexamined Patent Application, First Publication No. S61-121590 proposes an endoscope system utilizing a method in which video signals of the image pickup device are A/D-converted at the distal end portion of an endoscope and the digitized video signals are transmitted through the endoscope. If only High level and Low level of the signals are identified, video images will not be scrambled even if the digitized video signals are influenced by noise. Therefore, resistance to noise is improved.
In recent years, image pickup devices tend to be provided with higher resolution, resulting in an increase in the amount of data in signals. With this tendency, there is a demand for a higher transmission rate. In addition, there arises a need to set the amplitude of the digitized video signals small. As a result, even if video signals are digitized, conventional effects are less and less obtainable. Therefore, Japanese Unexamined Patent Application, First Publication, No. 2007-260066 proposes a technique of further converting the video signals, which have been A/D-converted at the distal end portion of the endoscope, to optical signals (performing E/O conversion), and then transmitting the video signals through an optical fiber.